Site Stats: migrating old site data to new site

I've been running a self-hosted WordPress blog since 2006 at a particular domain and for a variety of reasons, the time has come to use a different domain and refresh the site design.

I've managed to migrate all the data in the database, comments etc to the new site's database but I can't work out how to get my Jetpack dashboard to carry the old site stats across to the new address and set-up.

Both are listed in my WordPress.com account but I can't work out how to merge the two, or tell Jetpack that the new one should look to the old one for historic data.